To control and minimize fire during aircraft accidents it is common practice to employ crashworthy conduits and fittings with fuel systems. Such crashworthy devicds usually include self sealing valves and fittings having frangible components, and examples of such fittings and couplings are shown in U.S. Pat. Nos. 3,542,047; 3,719,194; 3,797,510; 3,913,603, and 4,119,111. Crashworthy couplings and fittings commonly utilize predetermined tension forces to trigger the sealing of the coupling or fitting upon impact.
Aircraft using adjacent fuel cells normally employ conduit systems interconnecting the fuel cells which are of a crashworthy construction. A common installation consists of two sets of self sealing valved couplings associated with a hose interconnecting the fuel cells with a frangible link existing at each fuel tank. Such an installation while permitting a degree of flexibility and misalignment between adjacent fuel cells, requires considerable space and separation between the fuel cells, and is expensive in that four self sealing valves are utilized.
Aircraft fuel cells have also been interconnected with rigid frangible self sealing valved fittings, but the rigidity of such systems is undesirable in that the cells must be closely and accurately positioned, and there is no flexibility to such a system to compensate for misalignment which often occurs during aircraft construction and fuel tank installation.
In crashworthy conduit systems interconnecting fuel cells tension members, such as cables, sheaths, or links are sometimes used to close the valves of the couplings as the fuel cells are displaced relative to each other during impact, and the use of such extraneous apparatus adds expense to the apparatus, and often complicates installation.
It is an object of the invention to provide a flexible hose and valved fitting assembly which can be used with aircraft fuel cells, or any installation, wherein it is desired to seal valves upon a predetermined tension existing within a flexible hose interconnecting the valved fittings.
A further object of the invention is to provide an intertank valve assembly utilizing identical fittings employing self sealing valves wherein the fittings are interconnected by a flexible hose to simplify assembly and installation by compensating for misalignment problems, and wherein a relatively short hose may be employed in a relatively concise space, and yet, the sequence of operation assures the closing of the fitting valves prior to hose rupture.
An additional object is to provide a flexible hose and self sealing valved fitting assembly utilizing frangible elements wherein a predetermined tension within the hose less than the hose rupture tension force will fracture the frangible elements releasing the fitting valves to a closed condition, and operation of the valves triggering apparatus is assured prior to hose rupture.
A further object of the invention is to provide a crashworthy flexible hose and self sealing valved fitting assembly wherein actuation is produced upon a predetermined tension existing within the hose, and wherein no tension devices other than the hose itself interconnects the spaced fittings.
In the practice of the invention a self sealing valved fitting is loated upon each end of a short flexible hose. Each fitting is adapted to be mounted in the wall of a fuel cell, and a mounting flange is associated with the fittings for this purpose. Ports are defined in the fitting, and a spring biased valve within the fitting is normally held in the full open position by a trigger mechanism.
Each fitting includes a nipple having a portion received within the hose, and the nipple is mounted within the fitting in such a manner that, upon the fracture of a frangible element, limited displacement between the nipple and fitting occurs in the direction of tension forces existing within the hose. A radially extending frangible rib is defined up on the nipple and the rib is in axial alignment with an abutment formed in the fitting engaging the rib. Upon a tension force existing within the hose which is less than the force which will rupture the hose the abutment will fracture the rib permitting sufficient nipple movement to actuate the associated valve trigger causing the spring biased valve to immediately close. The abutment prevents further relative movement between the nipple and fitting until the tension forces within the hose considerably exceed that necessary to fracture the ribs of both nipples whereby the valves within both fittings will close prior to rupture of the hose, or complete separation of a nipple and a fitting. Thus, the valves within the fittings will be closed prior to a condition existing wherein fuel may spill from the hose or fitting.
The nipple is provided with an axially extending cylindrical surface engaged by an O-ring carried by the fitting body wherein initial relative movement between the nipple and fitting to trigger the associated valve does not break a sealed relationship between the nipple and fitting, and the disclosed structure assures that the fitting valves will be closed prior to the interior of the assembly being exposed to the atmosphere.